Artificial cervical and lumbar disc system

ABSTRACT

An artificial replacement disc includes a pair of substantially parallel plates formed to occupy a space defined by vertebral endplates, each of the plates including a plurality of spikes on a first surface and a concave trough formed on a second surface opposite of the first surface. A mobile core includes a core rim with opposing convex surfaces extending from opposite sides of the core rim, the mobile core being capable of being disposed between the pair of plates to permit the vertebral endplates to move relative to one another. The spikes on each of the plates extend substantially away from the mobile core and the convex surfaces are formed to integrally fit within the concave trough of at least one of the plates. The core rim limits lateral movement of the mobile core relative to the parallel plates. One or more insertion tools for inserting and implanting the replacement disc are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional Application 60/788,720 filed on Apr. 4, 2006, copending U.S. patent application Ser. No. 11/019,351, filed on Dec. 23, 2004 and Ser. No. 10/964,633, filed on Oct. 15, 2004, U.S. Provisional Application Nos. 60/578,319 filed on Jun. 10, 2004, 60/573,346 filed on May 24, 2004, 60/572,468 filed on May 20, 2004, 60/570,837 filed on May 14, 2004, and 60/570,098 filed on May 12, 2004, and U.S. patent application Ser. No. 11/487,415 filed on Jul. 17, 2006, the entire contents of all of the above identified patent applications are hereby incorporated by reference.

BACKGROUND

This description relates to a three piece mechanical total cervical artificial disc , which includes two spiked cervical plates and a mobile core. The disc may be inserted into the cervical intervertrebral disc space using a novel disc plate insertion gun which performs sequential single plate intervertebral implantation enabling symmetric bi-disc plate alignment for inter plate mobile core placement. This cervical disc design and method of implantation avoid the cumbersome and arduous implantation techniques of many other artificial cervical disc designs improving safety, improving bone-plate insertion/integration, allowing multiple-level disc placement, preserving vertebral body integrity, eliminating the need for excessive disc space distraction, and decreasing procedure length. This description also relates to a modified application of the disc plate inserter design from copending, related applications describing posterior placed total artificial disc (PTTLAD). The modified disc plate inserter allows posterior lumbar sequential placement of two opposing disc plates rather than simultaneous two disc plate placement as outlined in our previous publication. The modified disc plate inserter enables implantation of the PTTLAD into narrower lumbar disc spaces which were not accessible with our previous lumbar disc plate inserter.

Cervical and lumbar discs are entering the clinical neurosurgical and orthopedic markets. The benefits of these artificial discs are well known and have been thoroughly reviewed in our prior and co-pending prosthetic disc patents, including Provisional Application 60/788,720 filed on Apr. 4, 2006, copending U.S. patent application No. 11/019,351, filed on Dec. 23, 2004 and Ser. No. 10/964,633, filed on Oct. 15, 2004, U.S. Provisional Application No. 60/578,319 filed on Jun. 10, 2004, 60/573,346 filed on May 24, 2004, 60/572,468 filed on May 20, 2004, 60/570,837 filed on May 14, 2004, and 60/570,098 filed on May 12, 2004, and U.S. patent application Ser. No. 11/487,415 filed on Jul. 17, 2006, the entire contents of each of which are hereby incorporated by reference. In one or more of the foregoing applications, we described four different cervical artificial disc embodiments which expanded in two or three-dimensions. This description presents an evolutionary simplification of these embodiments, e.g., with fewer small parts, which expand in only one dimension, and can be inserted very simply and efficiently. Accordingly, the advanced cervical disc design of the present application is a geometric modification of previous lumbar disc designs in one or more of the above-referenced patents, e.g., U.S. Patent Publication No. 2007/0198089 A1.

The cervical disc design of the present application differs from approaches of the background art which typically describe two-piece designs, e.g., as opposed to the three disc designs of the present application. In the two-piece designs, one piece consists of either an upper or lower cervical disc plate with a central trough to accommodate the opposing disc plate. The other piece, the opposing disc plate, has an incorporated dome shaped immobile core. The immobilized core is stationary and does not move. Semi-constrained artificial motion occurs as a result of the troughed plate movement against and around the immobilized core.

One or more of these designs are described in the following exemplary patent documents, including U.S. Pat. No. 5,314,477, filed Mar. 4, 1991 (Thierry Marnay), entitled “Prosthesis for intervertebral discs and instruments for implanting it;” U.S. Pat. No. 6,113,637 (Gill et al.), filed Oct. 22, 1998, entitled “Artificial intervertebral joint permitting translational and rotational motion; U.S. Pat. No 6,540,785 B1 (Gill et al.) filed on Mar. 24, 2000, entitled “Artificial intervertebral joint permitting translational and rotational motion;” U.S. Pat. No 6,8899,735 B2 (Bradley J Coates et. al.) filed on Oct. 2, 2002, entitled “Modular intervertebral prosthesis system,” U.S. Pat. No. 6,908,484 B2 (Zubok et. al.) filed on Mar. 6, 2003, entitled “Cervical disc replacement.” In each of the foregoing two-piece designs of the background art, the artificial implant is implanted within the vertebral bodies either by using attached hinges, keels or some form of extension which accommodates placement of vertebral screws.

The present inventors have determined that one disadvantage of most of these systems is that placement of the prosthesis is arduous, and time consuming, and can destroy a substantial part of the vertebral body after insertion of the device. The designs that use screws have the potential risks of screw pull out and secondarily esophageal injury, screw breakage, and/or inability to perform multilevel disc placement. Furthermore the fact that these designs do not have a mobile core leads to substantially constrained motion.

Similarly, U.S. Patent Publication No. 2007/0173936 A1 (Hester) filed on Jan. 23, 2006, describes a design which includes spikes, also includes a two-piece design with an immobilized core. One or more embodiments of the present application includes a mobile core which more closely simulates natural semi-constrained motion of a healthy cervical disc. U.S. Patent Publication No. 2005/0021146 A1 (de Villiers et al.) filed May 26, 2004 consists of two separate plates placed which are inserted simultaneously as one unit , after which a mobile core is inserted in between the plates. However, the plates include keels which can damage vertebral bodies, and prevent multilevel placement. U.S. Pat. No. 6,001,130 (Bryan), filed Oct. 6, 1997, describes a one piece design. However, the one-piece design involves an arduous placement technique involving disc space distraction, and the use of hinges and screws, limiting multi-level placement.

SUMMARY

One or more of the embodiments of the present application overcome one or more of the above-described shortcomings of the background art. For example, a cervical disc design and tool for implantation of the cervical disc is an improvement over one or more of the above mentioned designs of the background art. Specifically, the spikes allow integration into the vertebral body, e.g., with relatively small spikes, without damaging the vertebral bodies. This is particularly important if future prosthetic or fusions need to be performed at that level. The cervical plates are inserted sequentially with a novel cervical plate insertion gun. The advantage of the cervical plate insertion gun is that the method of implantation is quick and efficient. No disc space distraction is needed and hence there is no fear of damaging or disarticulating posterior cervical facets. It can also be placed into narrower spaces without distraction. The mobile core of the present application also more closely approximates the natural semi-constrained motion of a healthy disc more so than the above mentioned discs.

Additional advantages of our posterior placed total lumbar artificial disc (PTTLAD) lumbar disc design have been fully reviewed in our co-pending patents, each of which have been incorporated by reference herein. The present lumbar disc plate inserter design offers two additional advantages over previous embodiments. First, the inserter design grasps the plates more securely. In addition, the sequential placement of the different plates allows placement of posterior artificial discs into narrower disc spaces.

In one general aspect, an artificial spinal disc includes a pair of substantially parallel plates formed to occupy a space defined by vertebral endplates. Each of the plates including a plurality of spikes on a first surface and a concave trough formed on a second surface opposite of the first surface. A mobile core includes a core rim with opposing convex surfaces extending from opposite sides of the core rim, the mobile core being capable of being disposed between the pair of plates to permit the vertebral endplates to move relative to one another. The spikes on each of the plates extend substantially away from the mobile core and the convex surfaces are formed to integrally fit within the concave trough of at least one of the plates. The core rim limits lateral movement of the mobile core relative to the parallel plates.

Implementations of this aspect may include one or more of the following features. For example, the plates and mobile core can be sized and shaped to integrally fit within a space defined by cervical vertebral endplates and/or lumbar vertebral endplates. Each trough can be disposed in a center of each respective, parallel plate. The troughs can be shaped to receive the convex surfaces of the mobile core and the core rim can be shaped to receive outer edges of the troughs with an integral fit. The substantially parallel plates can include a plurality of conically shaped spikes.

The mobile core rim may include at least a first substantially ring shaped member having a raised edge and a second substantially ring shaped member having a raised edge. The first and second ring shaped members may each define respective cavities where the convex surfaces are respectively positioned within and extend from. The plates can comprise an elliptical shape.

In another general aspect, an artificial disc insertion system includes an artificial disc having a pair of substantially parallel plates formed to occupy a space defined by vertebral endplates, each of the plates including a plurality of spikes on a first surface and a concave trough formed on a second surface opposite of the first surface. The disc includes a mobile core having a core rim with opposing convex surfaces extending from opposite sides of the core rim, the mobile core being capable of being disposed between the pair of plates to permit the vertebral endplates to move relative to one another. The spikes on each of the plates extend substantially away from the mobile core and the convex surfaces are formed to integrally fit within the concave trough of at least one of the plates. The core rim limits lateral movement of the mobile core relative to the parallel plates. The system also includes a surgical tool.

The surgical tool for inserting the artificial disc between vertebral endplates, the tool includes a handle portion having a trigger, an upper disc plate release button, and a lower disc plate release button. The surgical tool also includes an insertion portion extending distally away from the handle portion, the insertion portion includes an upper replacement plate releasing portion and a lower replacement plate releasing portion. The upper replacement plate releasing portion includes a release handle and a release link configured to engage and release a periphery of an upper replacement plate, e.g., to releasably secure the upper replacement plate therebetween. The lower replacement plate releasing portion includes a release handle and a release link configured to engage and release a periphery of a lower replacement plate, e.g., to releasably secure the lower replacement plate therebetween.

Implementations of this aspect may include one or more of the following features. For example, the mobile core and plates can be sized and shaped for a cervical disc replacement. The mobile core and the plates can be sized and shaped for a lumbar disc replacement. The mobile core rim may include at least a first substantially ring shaped member having a raised edge and a second substantially ring shaped member having a raised edge. The first and second ring shaped members may each define respective cavities where the convex surfaces are respectively positioned within and extend from. The plates can include an elliptical shape.

In another general aspect, a surgical tool for inserting an artificial disc between vertebral endplates includes a handle portion comprising a trigger, an upper disc plate release button, and a lower disc plate release button. The tool also includes an insertion portion extending distally away from the handle portion, the insertion portion comprising an upper replacement plate releasing portion and a lower replacement plate releasing portion. The upper replacement plate releasing portion includes a release handle and a release link configured to engage and release a periphery of an upper replacement plate, e.g., to releasably secure the upper replacement plate therebetween. The lower replacement plate releasing portion includes a release handle and a release link configured to engage a periphery of a lower replacement plate, e.g., to releasably secure the lower replacement plate therebetween.

Implementations of this aspect may include one or more of the following features. For example, the insertion portion may include an upper tip portion and a lower tip portion. The upper tip portion and the lower tip portion may be curved to facilitate posterior insertion of a lumbar replacement disc in a patient. At least one of the upper or lower replacement plate releasing portions can include a leaf spring, a tension cable and a wedge portion proximally disposed relative to the respective release handle and the release link. Each of the upper and lower replacement plate releasing portions can include a leaf spring, a tension cable and a wedge portion proximally disposed relative to the respective release handle and the release link. The tool can include a replacement disc plate driver portion for driving a replacement disc plate from a first, proximal position toward a second, distal position. The upper replacement plate releasing portion is configured to secure an upper replacement plate in a position opposite from and axially aligned with a center of a lower replacement plate held within the lower replacement releasing portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an anterior (or posterior) view of an exemplary cervical artificial disc.

FIG. 1B is an isometric view of the cervical artificial disc of FIG. 1A.

FIG. 1C is an exploded view of the cervical artificial disc of FIG. 1A.

FIG. 1D is a superior (or inferior) view of the cervical artificial disc of FIG. 1A.

FIG. 2A is a side view of an exemplary cervical artificial disc mobile core.

FIG. 2B is an isometric view of the exemplary cervical artificial disc mobile core.

FIG. 2C is a front (or back) view of the exemplary cervical artificial disc mobile core.

FIG. 3A is a side view of an exemplary cervical artificial disc superior or inferior plate.

FIG. 3B is a top oblique-trough side view of the exemplary cervical artificial disc superior or inferior plate.

FIG. 3C is a top oblique-spike view of the exemplary cervical artificial disc superior or inferior plate.

FIG. 3D is a front-trough side view of the exemplary cervical artificial disc superior or inferior plate.

FIG. 3E is a front-spike side view of the exemplary cervical artificial disc superior or inferior plate.

FIG. 4A is a cross-sectional view of a cervical disc core showing the angular movements about the x-axis of the cervical disc core with respect to the upper and lower cervical plates (lateral bending).

FIG. 4Bi is a front view of later cervical disc bending.

FIG. 4Bii is a side view of flexion/extension cervical artificial disc motion.

FIG. 4Ci is a front view of the artificial disc showing the rotations of the mobile core between the two cervical disc plates about the x-axis (lateral bending or roll).

FIG. 4Cii is a side view of the artificial disc showing the y-axis (flexion/extension or pitch).

FIG. 4Ciii is a perspective view of the artificial disc showing the z-axis (rotation or yaw).

FIG. 5A is a front view of a cervical disc plate insertion gun.

FIG. 5B is a top view of the cervical disc plate insertion gun.

FIG. 5C is a bottom view of the cervical disc plate insertion gun.

FIG. 6A is a perspective, left-side, cut-away view of the cervical disc plate insertion gun.

FIG. 6B is a left side, bottom angle view of the cervical disc plate insertion gun.

FIG. 6C is a right side, top angle view of the cervical disc plate insertion gun.

FIG. 6D is a right side, bottom angle view of the cervical disc plate insertion gun.

FIG. 6E is a cut-away view of the tool tip lower cervical disc replacement plate release mechanism.

FIG. 7A is a view of an outside left enclosure of the cervical disc plate insertion gun.

FIG. 7B is a view of an inside left enclosure of the cervical disc plate insertion gun.

FIG. 7C is a view of an outside right enclosure of the cervical disc plate insertion gun.

FIG. 7D is a view of an inside right enclosure of the cervical disc plate insertion gun.

FIG. 8A is a top view of inner components of the cervical plate insertion gun including the lower insertion handle.

FIG. 8B is a lower insertion handle bottom view.

FIG. 8C is top view of a lower insertion link.

FIG. 8D is bottom view of the lower insertion link.

FIG. 8E is a view of the wedge link.

FIG. 8F is a top view of the upper insertion handle.

FIG. 8G is a lower view of the upper insertion handle lower view.

FIG. 8H is a close-up bottom view of a rear portion of the upper insertion handle.

FIG. 8I is a close-up, top view of a forward portion of the upper insertion handle.

FIG. 8J is a top view from left of the upper insertion release link.

FIG. 8K is a top view from a right side of the upper insertion link.

FIG. 8L is a view of a manual upper disc replacement plate driver.

FIG. 8M is a view of a trigger spring.

FIG. 8N is a view of a trigger.

FIG. 8O is a view of a wedge.

FIG. 9A is a perspective cut away view of an exemplary lumbar disc plat insertion gun.

FIG. 9B is a cut-away view of the tool tip of the lower lumbar disc replacement plate release mechanism.

DESCRIPTION OF PREFERRED EMBODIMENTS The Medical Device of FIG. 1-9.

Referring now to FIGS. 1-9, the above described problems of the background art can be solved in the cervical spine (and lumbar spine) after the performance of an anterior complete cervical discectomy. The disc device 10 includes an upper cervical plate 100 and lower cervical plate 110, one of which is inserted first by a plate insertion gun 500. The opposite (second) cervical disc plate 110 is then inserted with the plate insertion gun 500 maintaining parallel opposition, with opposite plates 100, 110 and troughs 102, 112 perfectly aligned. A mobile core 150 is then inserted and sandwiched in-between both cervical plates 100, 110.

FIGS. 1A-D illustrate different views of the cervical artificial disc 10. The disc 10 includes an upper plate 100 and a lower plate 110. Each plate has a plurality of spikes 101, 111, e.g., six spikes 101, 111 on each plate in a preferred embodiment, on an outer surface of the respective plate, and a centralized trough 102, 112 on an inner surface of each plate 100, 110.

FIGS. 2A-C illustrate different views of the cervical mobile core 150. The core 150 has a centralized base rim 151 with a superior convexity 152 which interacts with the trough 102 of the upper plate 100, and an inferior convexity 153 which interacts with the trough 112 of the lower plate 110.

FIGS. 3A-E illustrate different views of the cervical plate (superior or inferior) 100 (110). The plate 100 includes a base 114. On an upper surface of the inferior plate 110 is a trough 112. On a lower surface of the inferior plate 110 are 6 peripherally arranged spikes 111. The position of the trough 112 and spikes 111 are reversed for the superior plate (100). A groove 113 is defined by the trough 112 (102) and base 114 (104) of each plate 110 (100).

FIG. 4A illustrates a cross-sectional view of the cervical artificial disc 10 and the degrees of motion of the mobile core 150 movement about the x-axis with respect to the upper plate 100 and lower plate 110. Each disc plate 100 can bend about the x axis by 4.39 degrees clockwise and counter-clockwise (lateral bending). This means that a disc plate 100, 110 can move − or +8.78 degrees with respect to the opposite plate 110, 100.

FIG. 4B illustrates a front view of lateral bending of the artificial disc 10 (FIG. 4Bi), and a side view illustrating flexion-extension of the cervical disc 10 about the y axis which is 4.39 degrees in either flexion or extension.

FIG. 4C illustrates the rotation of the mobile core 150 between two cervical plates 100, 110 about the x (FIG. 4Ci), y (FIG. 4Cii) and z (FIG. 4Ciii) axes. Rotation about the x-axis is referred to as roll (alpha) which is lateral bending. Rotation about the y axis is referred to as pitch (Beta) which is flexion/extension. Rotation about the z axis is referred to as yaw (gamma) which is axial rotation. These figures display different views that show a reference frame for the disc assembly 10 with an origin O at the center of the core 150. The axes of rotation pass through the spherical face of the core 150 which is lower than 0 but are parallel to both the x and y axes. The rotation of the disc plates 100, 110 about the z-axis is constrained only by the spine motions once the disc 10 is implanted.

FIGS. 5-8 illustrate the components of the cervical disc plate insertion gun 500. Various opening mechanism functions will be described in greater detail hereinafter with respect to FIGS. 5-8. The handle 512 of the opening mechanism is made up of left and right enclosures 501, 502 (FIGS. 5, 6, and 7). FIG. 7 illustrates the inside and outside aspects of left and right enclosures 501, 502. These enclosures 501, 502 are held together by five enclosure fastening screws 590 (FIG. 6B). The handle 512 holds the mechanism used to insert the upper disc plate 100 and lower disc plate 110 (FIGS. 5-6, and FIG. 8) into the vertebrae. The mechanism has two functions, including: 1) Holding onto the disc plates 100, 110 until the user releases them, and 2) opening the tip 560 and forcing one disc plate at a time into a vertebra.

1. Holding onto the Discs Until User Releases them

The mechanism has two tips 565, 580 each holding a disc plate 100, 110. The lower tip 580 is composed of two parts: the lower insertion release link 576 and the lower insertion release handle 551 (FIGS. 6 and 8). The upper tip 565 includes two parts: the upper insertion handle 550 and the upper insertion link 575 (FIGS. 6 and 8). Each tip 565, 580 works like a “lobster claw” that holds a disc plate by the “groove” 552 on its cylindrical extrusion. When the tip 565, 580 is closed the two opposing parts e.g. the lower insertion release link 576 and the lower insertion release handle 551 (FIGS. 6 and 8) hold a disc plate 110 firmly.

A tip 580 opens to release a disc plate as follows. A lower tension cable 571 pulls on the lower insertion release link 576 (FIGS. 6 and 8) that pivots about the lower release pin 598 (FIG. 6) and opens up a gap big enough to loosen the grip on the disc groove 552. The lower tension cable 571 (FIG. 6) can only exert a tensile force to open the lobster claw 580. The natural state of the lobster claw 580 is to be closed. This is ensured by pre-loading the lower insertion release link 576 with the help of a leaf spring 599 cut into the lower insertion release handle 551 (FIGS. 6E and 8). The lower tension cable 571 pulls on the lower insertion release link 576 (FIGS. 6 and 8) each time the user presses on the lower release button 540. The lower tension cable 571 is clamped on one end by a lower rear crimp 592 (FIGS. 6 and 8). Hence when the lower release button 540 is pressed, the tension on the lower tension cable 571 increases (in the same way the tension of a guitar string increase when one presses on the string with a finger). The tension then pulls the lower insertion release link 576 forcing it to swing open. When the user lets go of the button 540, the tension disappears and the spring 599 carved in the lower insertion release handle 551 forces the lower insertion release link 576 to swing closed (FIG. 6E).

The upper tip 565 works in a similar fashion except that its opening is triggered by the upper release button 530.

2. Opening its Tip and Forcing One Disc at a Time into a Vertebra

The mechanism tips 565, 580 open each time the user presses on trigger 510. When the trigger 510 rotates, it pushes on the wedge link 513 which in turn pushes on the wedge part 525 (FIG. 8). The wedge part 525 is wedged at its front action end that creates a gap in between the lower tool tip 580 and upper tool tip 565 forcing them to open.

A typical disc insertion operation starts with a lower disc plate 110 placed in the lower tip 580 and the opposing upper disc plate 100 placed on the upper side but away from the tip 565 (as shown in FIGS. 5,6, and 8). A channel 553 along the upper tip 565 that is formed by the upper insertion release handle 550 and the upper insertion release link 575 which holds the second disc plate 100 in place and serves to guide it to the tip 565 when needed.

Once the tool tip 560 is inserted into the inter-vertebral space, the first disc plate 100 is inserted into the lower vertebra by opening the tool tip 560. To keep alignment, the lower tool tip 585, “lower lobster claw”, is kept closed (FIG. 6), securing the disc plate just inserted. The tool 500 should be left in place. The second, upper, disc 100 initially placed in the upper tool half, away from the “upper lobster claw” 565 but away from the tip is then slid down to the end of the upper lobster claw 565 by a flexible and manually activated upper disc replacement plate driver 520 (FIGS. 6 and 8). Once the second disc 100 is positioned at the tip of the upper “lobster claw” 565 (FIG. 6), the tool tip 560 is opened once more, i.e., the upper tip 565 and lower lobster claw tip 580 are separated from each other, by virtue of the wedge 525 that is activated by the trigger 510, via wedge link 513 action. Once the second, upper, disc plate 100 is inserted, the user can press on the upper release button 530 and lower release button 540 to release both discs (by opening the upper and lower “lobster claws” 565, 580) and at the same time close the tool tip 560 (by releasing the trigger 510). The tool tip 560 then closes while both “lobster claws” 565, 580 remain open, leaving both disc plates 100, 110 in place. The tool tip 560 can then be removed from the patient and a mobile core placed in between the two aligned disc plates 100, 110.

This anterior cervical disc gun can be modified and enlarged for placement of anterior lumbar disc plates. FIG. 9A illustrates the modified posterior lumbar disc plate insertion gun 700. The gun 700 is identical to the cervical disc plate insertion gun 500 except its tips 660 are angled to allow insertion of the specifically sized lumbar disc plates 100, 110 in the posterior lumbar spine underneath the thecal sac.

FIG. 9B illustrates an enlarged cut-away view of the tool tip 660 of the lumbar lower disc replacement plate release mechanism 670. The mechanism 670 is identical to that described for the cervical mechanism which is illustrated FIG. 6E. The tips 660 of the lumbar tool are however, specifically designed and adapted for the typically bean shaped lumbar disc plates.

The Surgical Method

The method of insertion of the cervical artificial disc (or lumbar artificial disc) into the anterior cervical spine can be performed open microscopically, or closed tubularly, using endoscopic and/or fluoroscopic guidance.

After the adequate induction of anesthesia the patient is positioned in the supine position. Routine exposure of the anterior cervical spine is performed and the appropriate disc space is radiographically identified and exposed. A routine complete anterior cervical discectomy is performed.

The cervical disc plates are inserted onto the cervical disc plate insertion gun 500. The tips 560 of the gun 500 are placed into the intervertebral space. Fluoroscopy is used to assure centrality of disc plate placement.

The trigger 510 of the gun 500 is depressed and the bottom plate 110 is inserted into the lower vertebrae. Once this penetrates the bone, the lower plate releasing button 540 is depressed, thereby releasing the plate from the inserter claws 580 (FIG. 6E) . The second upper plate 100 is now manually driven into the space by the gun's manual plate driver 520. Because of the design of the gun 500, the upper plate 100 is perfectly aligned with the lower plate 110. The gun trigger 510 is depressed and this drives the upper plate 100 into the upper vertebrae. The upper plate releasing button 530 is now depressed, releasing the upper plate 100 from the inserter lobster claws 565. The gun 500 is removed from the interspace. A mobile core 150 of the appropriate height is selected and placed in between the upper and lower cervical disc plates 100, 110, respectively. The patient is closed routinely.

The surgical method for the posterior insertion of the PPLTAD into the posterior lumbar interspace can be performed open microscopically, or closed tubularly, using endoscopic and or fluoroscopic guidance.

After the adequate induction of anesthesia the patient is positioned in the prone position. A midline incision is made, the appropriate unilateral lamina is radiographically identified and exposed, and a unilateral hemi-laminotomy is performed preserving facet stability. A complete discectomy is performed, and the superior and inferior endplates are exposed. The lumbar pplate insertion gun 700 is placed underneath the thecal sac. Fluoroscopic guidance may be used to verify centrality of lumbar disc plate placement. The trigger of the gun 700 is depressed which leads to insertion of the lower lumbar disc plate 100 into the lower vertebra. The lower lumbar disc plate releasing button is depressed which releases the plate from the inserter claws 551 (FIG. 9B). The second upper plate 100 is now manually driven into the interspace by the gun's 700 manual plate driver (520). Because of the design of the gun mechanism as described above, the second plate 100 is now perfectly aligned with the first lumbar disc plate 110. The gun trigger is depressed, and this drives the upper plate 100 into the upper vertebrae. The upper lumbar disc plate release button is now depressed and this releases the upper lumbar disc plate from the claws of the inserter gun 700. The gun 700 is removed from the space. An appropriately sized mobile core 150 is now inserted in between upper and lower lumbar disc plates 100, 110. The patient is closed routinely.

The current device allows safe placement of lumbar and cervical artificial discs into the spine without intervertebral distraction, and therefore places minimal tension on facet joints. The method of insertion is quick, gentle, and time efficient. The plate insertion gun could potentially be adapted for other inter joint orthopedic devices, and further adaptations may have applications in manufacturing, toy, carpentry and other industries. 

1-20. (canceled)
 21. An artificial disc system comprising: an artificial disc comprising: first and second plates formed to occupy a space defined by vertebral endplates of a spine, each of the first and second plates including an endplate-engaging surface having a plurality of anchors and a core-engaging surface positioned opposite the endplate-engaging surface, wherein the plurality of anchors on the endplate-engaging surface of the first plate comprise a first group of at least three anchors on a left side of the first plate and a second group of at least three anchors on a right side of the first plate with a middle portion of the first plate having no anchors between the first and second groups of anchors, wherein the plurality of anchors on the endplate-engaging surface of the second plate comprise a third group of at least three anchors on a left side of the second plate and a fourth group of at least three anchors on a right side of the second plate with a middle portion of the second plate having no anchors between the third and fourth groups of anchors; and a mobile core sized and configured to be positioned between the first and second plates to permit the first and second plates to move relative to one another, wherein the anchors on the endplate-engaging surface extend away from the mobile core, wherein the core-engaging surfaces engage first and second plate-engaging surfaces of the mobile core, wherein at least one of the first and second plate-engaging surfaces are configured to slide against adjacent core-engaging surfaces of the first or second plate, wherein the first plate-engaging surface of the mobile core has a convex portion, and wherein the mobile core is engaged with the first and second plates such that the first plate can move with respect to the second plate about an x-axis for lateral bending, a y-axis for flexion/extension, and a z-axis for axial spinal rotation, wherein the mobile core is sized large enough to extend partially out of a space defined between the first and second plates when the artificial disc is tilted about the y-axis for flexion/extension.
 22. The artificial disc system of claim 21, wherein the core-engaging surface of the first plate is substantially concave.
 23. The artificial disc system of claim 22, wherein the convex portion of the mobile core is shaped as a spherical dome and is configured to mate with the substantially concave core-engaging surface of the first plate.
 24. The artificial disc system of claim 23, wherein the mobile core is configured to slide against the substantially concave core-engaging surface of the first plate.
 25. The artificial disc system of claim 24, wherein the mobile core comprises a core rim having a circular perimeter shape.
 26. The artificial disc system of claim 25, wherein the convex spherical dome portion of the mobile core extends from a first side of the core rim and is disposed within a perimeter of the core rim.
 27. The artificial disc system of claim 21, wherein at least one of the core-engaging surfaces of the first plate or the second plate comprises a ridge configured to limit a movement of the mobile core on the core-engaging surface.
 28. The artificial disc system of claim 21, further comprising: a surgical tool for inserting the artificial disc between vertebral endplates, the surgical tool comprising: a handle portion; an elongate insertion portion extending distally away from the handle portion; and an implant holder connected at a distal end of the elongate insertion portion, the implant holder configured to engage the first and second plates of the artificial disc.
 29. The artificial disc system of claim 28, wherein the first plate, the second plate, and the mobile core are sized and shaped to fit within a space defined by cervical vertebral endplates.
 30. An artificial spinal disc, comprising: a pair of plates formed to occupy a space defined by vertebral endplates, each of the pair of plates having a first surface and a second surface opposite of the first surface, each of the pair of plates having at least one protrusion formed on the first surface, each of the pair of plates having a concave trough formed in the second surface; and a mobile core having a curved perimeter shape defined by a core rim extending from a first convex surface to a second convex surface, the mobile core disposed between the pair of plates and received in the concave trough of each of the pair of plates, wherein the second surface of each of the pair of plates is configured to slide against the first or second convex surface of the mobile core, thereby permitting movement of the pair of plates relative to one another, wherein the core rim limits the relative movement of the pair of plates; wherein the at least one protrusion on each of the pair of plates extends away from the mobile core, the at least one protrusion on each of the pair of plates configured to engage a vertebral endplate, wherein the at least one protrusion of at least one of the pair of plates includes a base portion and an end portion narrower than the base portion, wherein the end portion is configured to penetrate at least one surface of the vertebral endplates.
 31. The artificial spinal disc of claim 30, wherein the pair of plates and the mobile core are sized and shaped to fit within a space defined by cervical vertebral endplates.
 32. The artificial spinal disc of claim 30, wherein the at least one protrusion comprises at least two protrusions formed in a middle region of the first surface of each of the pair of plates.
 33. The artificial spinal disc of claim 32, wherein the at least one protrusion further comprises at least two protrusions formed at perimeter edges on either side of the middle region of the first surface of each of the pair of plates.
 34. The artificial spinal disc of claim 30, wherein at least one concave trough comprises a perimeter ridge about the concave trough.
 35. The artificial spinal disc of claim 34, wherein the core rim is shaped to receive the perimeter ridge at the outer edges of the at least one concave trough.
 36. The artificial spinal disc of claim 35, wherein the perimeter ridge at the outer edges of the at least one concave trough engages the core rim and limits a movement of the mobile core relative to the pair of plates.
 37. The artificial spinal disc of claim 30, wherein at least one of the opposing convex surfaces extending from opposite sides of the core rim is shaped as a spherical dome configured to fit the concave trough of at least one of the pair of plates.
 38. The artificial spinal disc of claim 30, wherein the at least one protrusion on a first surface of a first plate of the pair of plates further comprises a first group of at least three anchors positioned in a left region to a left side of the middle region of the first surface, and a second group of at least three anchors positioned in a right region to a right side of the middle region of the first surface.
 39. The artificial spinal disc of claim 38, wherein the at least one protrusion on a first surface of a second plate of the pair of plates further comprises a third group of at least three anchors positioned in a left region to a left side of the middle region of the first surface, and a fourth group of at least three anchors positioned in a right region to a right side of the middle region of the first surface.
 40. An artificial cervical disc comprising: first and second plates formed to occupy a space defined by cervical vertebral endplates of a spine, each of the first and second plates including an endplate-engaging surface having a plurality of anchors and a core-engaging surface positioned opposite the endplate-engaging surface, wherein the plurality of anchors on the endplate-engaging surface of the first plate comprise a first group of at least three anchors on a left side of the first plate and a second group of at least three anchors on a right side of the first plate, wherein the plurality of anchors on the endplate-engaging surface of the second plate comprise a third group of at least three anchors on a left side of the second plate and a fourth group of at least three anchors on a right side of the second plate; and a mobile core sized and configured to be positioned between the first and second plates to permit the first and second plates to move relative to one another, wherein the anchors on the endplate-engaging surface extend away from the mobile core, wherein the core-engaging surfaces engage first and second plate-engaging surfaces of the mobile core, wherein a convex portion on the first plate-engaging surface of the mobile core is configured to slide against a substantially concave core-engaging surface of the first plate, and wherein the mobile core is engaged with the first and second plates such that the first plate can move with respect to the second plate about an x-axis for lateral bending, a y-axis for flexion/extension, and a z-axis for axial spinal rotation, wherein the mobile core is sized large enough to extend partially out of a space defined between the first and second plates when the artificial disc is tilted about the y-axis for flexion/extension. 